dUTPase is the unique enzyme that catalyses the pyrophosphorolysis of dUTP, thus regulating the extent of uracil incorporation into DNA. Massive uracil incorporation may lead to cell death. dUTPase has therefore been recognized as a high-potential drug target in cancer, viral and bacterial disease control. The present proposal focuses on the Mycobacterium tuberculosis (MTB) dUTPase that plays a central role in the mycobacterial dTTP biosynthesis and thus it is likely to be essential for the viability of MTB. MTB is the pathogen that causes tuberculosis, which imposes an increasing global threat with the high-rate emergence of novel multidrug (MDR) and extensively drug-resistant (XDR) strains. Several research agendas (including one at NIH) articulated new measures needed for successful tuberculosis management, which involves intensive research on new drug targets and the development of novel drugs. The present proposal has three Specific Aims all directed towards the evaluation of MTB dUTPase as a valid tool in fighting tuberculosis: 1. Study of the effect of dUTPase functional ablation on the viability of Mycobacterium, 2. Elucidation of the enzymatic mechanism of MTB dUTPase with regards to the mechanistic differences between the human (host) and MTB (pathogen) dUTPases, 3) Determination of the catalytic role of the two structural elements that may be species-specifically targeted in dUTPase. To address the above issues, several transient kinetic and equilibrium enzymological as well as spectroscopical methods will be employed using wild- type and mutant MTB dUTPase enzymes. The physiological effect of functional ablation of dUTPase in Mycobycterium will be investigated in a non-pathogenic Mycobacterium model subjected to dUTPase gene replacement. The expected results of the proposed project will be highly useful in effective species-selective inhibitor design for MTB dUTPase and in the prediction of the in vivo mechanism of such inhibitors. The combination of approaches of this project (cf. Aims 1-3) may serve as a useful concept for the investigation of further potential dUTPase targets such as dUTPases from Plasmodium falciparum;Trypanosoma;vaccinia, herpes and Epstein-Barr viruses. PUBLIC HEALTH RELEVANCE The present proposal focuses on an important DNA repair enzyme called dUTPase of the bacterium causing tuberculosis. Tuberculosis imposes an increasing threat on global health. Therefore several research agendas (including a robust NIH program) articulated new measures needed for successful tuberculosis management, which involves the intensive research of physiological targets for new drugs. The aims of this proposal are directed towards the evaluation of dUTPase as a drug target in tuberculosis control.